On Tue, Mar 01, 2005 at 09:10:56AM -0500, Aaron Sherman wrote:

>  This is a contrived simplification, and fails to reproduce the problem,
>  but it gives you an idea of what I was doing. 5.8.3 does not produce the
>  same warning.

I guess is that it's this change, new in 5.8.3:

[ 21920] By: nicholas                              on 2003/12/16  23:32:48
        Log: Integrate:
             [ 21875]
             fix bug #24605.
             substr() wasn't working when used repeatedly on the same utf-8
             string.
     Branch: maint-5.8/perl
	   ! sv.c
	  !>  t/op/substr.t


Nicholas Clark